1. Field of the Invention
The present invention relates to a pixel structure, and more particularly, to a layout of thin film transistors (TFTs) of a pixel structure.
2. Description of the Prior Art
FIG. 1 is a regional schematic diagram of a conventional pixel structure. As shown in FIG. 1, the conventional pixel structure 120 mainly includes a TFT 122, a pixel electrode 124, a scan line 126, and a data line 128. The TFT 122 is electrically connected to the pixel electrode 124. Specifically, the TFT 122 includes a gate electrode 122a, a channel region 122b, a source electrode 122c, and a drain electrode 122d. The TFT 122 is bottom gate TFT, and the drain electrode 122d of the TFT 122 is electrically connected to the pixel electrode 124. The scan line 126 provides a voltage to the gate electrode 122a, and the data line 128 provides a voltage to the TFT 122 and further transmits the voltage to the pixel electrode 124 via the TFT 122 to offer a potential difference to the liquid crystal layer.
An area where the gate electrode 122a and the drain electrode 122d overlap with each other forms a gate-drain capacitor (Cgd) 10. The capacitance of the gate-drain capacitor 10 is directly proportional to the size of the overlapping area. Generally, factors such as errors in mask alignment or machinery vibration may cause the layout of the drain electrode 122d to be misaligned all around the front, back, left, and right directions when manufacturing a TFT. As a result, the area where the gate electrode 122a and the drain electrode 122d overlap with each other in a vertical direction may change accordingly, which further causes an alteration in the capacitance of the gate-drain capacitor 10. As the capacitance level of the gate-drain capacitor 10 changes, the pixel feed-through voltage will change as well, which may affect the TFT display quality. For example, as TFTs are applied to control pixel arrays of a display device, capacitance fluctuation could result in uneven brightness in different pixels at the same desired grey scale, and thus, the display brightness control could become inferior to expectation.
Therefore, it is desired to improve the TFT layout in order to solve the display quality problems resulted from capacitance fluctuation.